Due to competition in freight carrier services by rail, sea, and air, the trucking industry has been strongly concerned about the efficiencies of their own system. In recent years, the costs of truckage have increased as a result of increased fuel costs and mandated lower speed limits eventuating from fuel shortages. One approach to offsetting such increased costs is to decrease fuel consumption.
Fuel consumption of the freight-hauling truck tractor and trailer combinations in a function of weight, engine efficiency, and air drag. Since the freight capacity must be maintained at a high level in order to satisfy the economics of trucking, the size and, thus, the weight of the truck combinations cannot be decreased enough to result in substantial fuel savings. Of course, improvements in engine efficiency will always be made but they are not sufficient by themselves to eliminate the burden caused by weight and air drag. Air drag, especially between the tractor and the trailer and at the rear end of the trailer, is a very important cause of poor fuel consumption. A truck tractor and trailer combination that gets about four miles per gallon loaded, for example, may only get four and one half miles per gallon unloaded when operated at the same high speed. It is known that this mileage can be increased by placing an air deflector above the cab of the truck trailer. Redesign or modifications to present designs of truck tractor and trailer combinations would greatly reduce such air drag and, thus, reduce fuel consumption.